<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>成绩等级</title>
</head>

<body>
    <script>
        var score = prompt("请输入学生成绩：", 80);
        var grade = score >= 80 ? "A" : "B";
        alert("该学生成绩等级是：" + grade);
    </script>
</body>

</html>